Method for the recovery of nickel from mixed ores

ABSTRACT

Method for improving the recovery of nickel by magnetic separation of the product resulting from the treatment of a nickeliferous initial material by a segregation process, characterized in that the nickeliferous initial material is obtained by mixing laterite and a second type of ore in which the acid value, i.e., the ratio of the oxygen content of the silica contained in the ore to the oxygen content of the basic components of said ore, is greater than one.

0 United States Patent 1191 1111 3,801,306 Rey et al. Apr. 2, 1974 METHOD FOR THE RECOVERY OF 3,323,900 6/1967 Takahashi et al 75 2 NICKEL FROM MlXED ORES 1,480,212 1/1924 Lamothe 1 75/82 1,487,145 3/1924 Caron 75/82 X lnvemorsr Maurice y; Victor Ffll'manek, 2,573,153 10 1951 Lichty 75/82 x both of Paris, France 2,400,098 5/1946 Brogdon 75/82 [73] Assignees: Le Nickel; Societe Miniere Et OTHER PUBLICATIONS Metaulll'gioue De Penal'mya, both of Danas Manual of Mineralogy; 16th Ed.; John Wiley & Paris, France; part interest to each S New York; 1952; pages 351-353. [22] Filed: Sept. 27, 1971 Primary ExaminerL. Dewayne Rutledge PP N05 184,242 Assistant Examiner-M. J Andrews Attorney, Agent, or Firm-Fleit, Gipple & Jacobson [30] Foreign Application Priority Data Sept. 28, 1970 France 70.34961 [57] ABSTRACT Method for improving the recovery of nickel by mag- 52 US. Cl. 75/82 hetie Separation of the product resulting from the 51 Int. Cl 0220 23/02 treatment of e hiekelifereus initial material y e Segre- [58] Field of Search 75/82, 111, 113 getieh Process, characterized in that the hiekelifereus initial material is obtained by mixing laterite and a 5 References Cited second type of ore in which the acid value, i.e., the UNITED STATES PATENTS ratio of the oxygen content of the silica contained in 3 453 101 W196) T k h t I H X the ore to the oxygen content of the basic components a a as re a 2,400,461 5/1946 H1115 74/82 x of Sam gnaw than 3,656,935 4/1972 lwasaki 75/82 2 Claims, No Drawings METHOD FOR THE RECOVERY OF NICKEL FROM MIXED ORES BACKGROUND OF THE INVENTION The present invention relates to the recovery of nickel from oxide ores by the segregation process. It is well-known that this segregation process in general consists in reacting at a temperature between 900 and 1,000 C a finely comminuted mixture comprising nickeliferous ore, carbon and a chloridizing agent which is generally an alkali chloride, an alkaline earth chloride or a mixture of such chlorides.

Furthermore, the Applicants have shown in their copending US. Patent application Ser. No. 79,711 filed Oct. 9, 1970 for Ore Segregation Process, now abandoned, that these chlorides can be replaced by hydrochloric gas, by chlorine or by a gaseous mixture containing one or both of these gases.

Whatever chloridizing agent is used, the chemical reactions which occur during the segregation lead to the volatilization of nickel in the form of nickel chloride and to its precipitation as metal on the carbon particles. The metal which was disseminated in the oxides and silicates of the ore gangue segregates as discrete particles with a high nickel content which are then recovered by magnetic separation or by flotation to give a concentrate with a high metal percentage provided the operating conditions are appropriately chosen in which event the extraction of nickel can reach 80 to 90 percent, the remainder being essentially iron.

However, experiences have shown that one of the main types of nickel oxide ores, namely, laterite, the composition of which will be given below, is not very adapted to the magnetic separation which follows the segregation itself. But this magnetic separation method is preferred as it is economically much more advantageous than the flotation method and, furthermore, use of the magnetic separation method produces richer nickel concentrates and tailings which are poorer in nickel.

The superiority of the magnetic separation is further demonstrated by the fact that whenever the flotation is used, it is recommanded to treat the concentrate by magnetic separation to enrich it. Often even the tailings are subjected to a magnetic treatment to recover nickel and to make it poorer.

Accordingly, a serious problem of the art and one of great interest is to find a way to make laterite suitable to magnetic separation following a normal segregation treatment.

One of the objects of the present invention is thus to provide a process for the segregation treatment of laterite which allows an excellent subsequent magnetic separation.

Another object of this invention is the provision of a process of this type which leads to a high nickel percentage in the concentrate and to a low percentage of this metal in the tailings resulting from a magnetic concentration treatment.

A further object of this invention is to provide a method of the type described hereinabove which lowers the concomitant extraction of the iron contained in the ore, during magnetic separation.

BRIEF SUMMARY OF THE INVENTION These and other objects are accomplished according to the process of this invention by adding to laterite another type of nickel oxide ore like garnierite the composition of which will be given below, and subjecting to segregation and magnetic separation processes whereby the nickel content of the concentrate obtained by magnetic separation is surprisingly higher than when using, either laterite alone, or garnierite alone as the starting ore.

More generally, this surprising result is obtained, according to the invention by adding to laterite an ore with an acid index greater than one.

Preferably, such ore with an acidic reaction represents at least weight percent of the initial mixture and, advantageously and more preferably, about weight percent of this mixture.

DETAILED DESCRIPTION First, one must bear in mind that the acid index of an ore is the ratio of the oxygen content of the silica contained in the ore to the oxygen content of the basic components of said ore. The latter comprise essentially, in the case of nickel oxide ore, magnesia and ferrous oxide. The determination of this ratio for a given ore is easily arrived at by those skilled in the art.

The Table I below gives the chemical analysis of several laterites and garnierites weight percent and shows the acid index for each of these ores. One notices that this index is always smaller than one for the laterites and greater than one for the garnierites.

TABLEI Analysis of several laterites and garnierties A Laterites N Ni SiO MgO Fe PF I 1 PF Loss on ignition.

B Garnierites N Ni SiO MgO Fe PF 1 1 The ratio I (Oxygen of the silica/oxygen of the basic components) takes in account only the magnesia.

The ratio I takes also in account the ferrous oxide. The lime and the illlill'lliwgiwm are very low, have been neglected.

Tar the lateritesjongrheratio l has been calculated,

as being the only significant one.

The invention is based on the discovery that the addition to laterite of an ore with an acidic reaction improves markedly its behaviour during the magnetic separation subsequent to the segregation. A possible explanation of this phenomenon will be given below, but the Applicants do not wish to be limited by a particular theory.

It is belived that during the segregation, the iron present in the ore is reduced to the state of magnetite Fe O then progressively to the state of ferrous oxide FeO. The intermediary magnetite is belived to be an obstacle to a satisfactory magnetic separation, because it is ferromagnetic,

Thus, the addition of an ore with an acidic reaction like gamierite would appear to facilitate the decomposition of this magnetite yielding a ferrous silicate and would appear to modify the conditions of the reduction For the segregation, the carbonaceous agent was coke added before the precalcination (2.5 weight percent) and the chloridizing agent was anhydrous calcium chloride added before the segregation (6 weight percent).

Table 11 gives the weight percentage of nickel and iron which were extracted during the magnetic separa tion subsequent to the segregation treatment described above. It also indicates the composition of the concentrates and tailings obtained.

: One notices that the addition of gamierite according to the invention leads, after the extraction, to a Ni/Fe ratio, which is much higher than the ratio observed, either in the case of laterite alone, or in the case of garnierite alone.

WEEEYEstilts were obi ned yvlieiifieproportioh of gamierite in the starting mixture was higher than 50 weight percent, and especially when this proportion was about 75 weight percent.

SEGREGATION (60 min. at 980C) Starting Mixture Concentrate Tailings Extraction Wt '51 Ni% Fe% Ni% Fe% Ni% Ni% Fe% Ni/Fe Garnierite in the Mixture SAMPLES A (1) SAMPLES B (2) (1) Precalcination 15 minutes at 1.000 C. (2) Precalcination 60 minutes at l.O00C.

during the segregation while making instable the magnetite which is formed.

Whatever the reasons which one could imagine to cause or lead to this surprising effect the plain fact is that it happens. In order that the invention may be well understood, an example will now be given to show, though by way of illustration only, the process herein described.

EXAMPLE What we claim is: 1. In a method for improving the recovery of nickel from laterite in which a. the laterite is subjected to a segregation process including heating a finally comminuted mixture of the laterite together with carbon and a chloridizing agent to about 900 to 1,000 C in order to produce a volitization of the nickel in the form of nickel chloride and thereafter the precipitation of the nickel on the carbon and b. the segregation product so produced is subjected to magnetic separation to recover a concentrate with a high content of nickel,

the improvement comprising admixing with said laterite at least about 50 percent by weight of gamierite.

2. The process of claim 1 wherein about percent by weight of gamierite is admixed with said laterite. 

2. The process of claim 1 wherein about 75 percent by weight of garnierite is admixed with said laterite. 